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<title>RTL Declarations (GNU Compiler Collection (GCC) Internals)</title>

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<h3 class="section" id="Declarations-2"><span>14.14 Declarations<a class="copiable-link" href="#Declarations-2"> &para;</a></span></h3>
<a class="index-entry-id" id="index-RTL-declarations"></a>
<a class="index-entry-id" id="index-declarations_002c-RTL"></a>

<p>Declaration expression codes do not represent arithmetic operations
but rather state assertions about their operands.
</p>
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<dt><a class="index-entry-id" id="index-subreg_002c-in-strict_005flow_005fpart"></a>
<a id="index-strict_005flow_005fpart"></a><span><code class="code">(strict_low_part (subreg:<var class="var">m</var> (reg:<var class="var">n</var> <var class="var">r</var>) 0))</code><a class="copiable-link" href="#index-strict_005flow_005fpart"> &para;</a></span></dt>
<dd><p>This expression code is used in only one context: as the destination operand of a
<code class="code">set</code> expression.  In addition, the operand of this expression
must be a non-paradoxical <code class="code">subreg</code> expression.
</p>
<p>The presence of <code class="code">strict_low_part</code> says that the part of the
register which is meaningful in mode <var class="var">n</var>, but is not part of
mode <var class="var">m</var>, is not to be altered.  Normally, an assignment to such
a subreg is allowed to have undefined effects on the rest of the
register when <var class="var">m</var> is smaller than &lsquo;<samp class="samp">REGMODE_NATURAL_SIZE (<var class="var">n</var>)</samp>&rsquo;.
</p></dd>
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